1. Field of the Invention
The present invention relates generally to an electronic apparatus having a coaxial semiconductor element module, and more particularly to an optical transmitter/receiver having as its basis configuration a coaxial optical semiconductor module, a photoelectronic circuit board, and an electrically conductive casing for electromagnetically shielding the circuit board, and used in, for example, an optical communication system executing transmission/reception and conversion of optical/electrical signals.
2. Description of the Related Art
FIG. 9A is an exploded view showing an example configuration of a typical optical transmitter/receiver 900; FIG. 9B is a side elevational view of the optical transmitter/receiver 900 illustrated in FIG. 9A; FIG. 9D is a front elevational view of the optical transmitter/receiver 900 illustrated in FIG. 9A. The optical transmitter/receiver 900 comprises a coaxial optical semiconductor element module 6; an electronic circuit board 7 electrically connected to the optical semiconductor element module 6 and having pads 8a and 8b on its surface; an electrically conductive casing 9 in the form of, e.g., a sheet metal box, which accommodates and electromagnetically shields the electronic circuit board 7; and a metal flange 10 interposed between the optical semiconductor element module 6 and the electrically conductive casing 9, a metal flange 10 being fitted with the optical semiconductor module 6 and fixedly secured to the electrically conductive casing 9 by means of screws 11a and 11b. The optical semiconductor element module 6 includes a stem 1 incorporating an optical semiconductor element; lead terminals 2a and 2b extending from the stem 1 for electrical connection with the optical semiconductor element; a can 3 partially covering the stem 1; a trunk 4 extending from the can 3; and a fiber 5 disposed on the trunk 4.
A conventional optical transmitter/receiver can be configured in the manner of the optical transmitter/receiver 900 described in the following. The electronic circuit board 7 is securely retained, for example by an adhesive, in the electrically conductive casing 9. The optical semiconductor element module 6 and the metal flange 10 are fixedly retained, for example by YAG welding. The electrically conductive casing 9 and the metal flange 10 are fastened together by screws or the like. The lead terminals 2a and 2b are connected to the pads 8a and 8b, respectively, for transmission/reception and conversion of optical/electric signals.
In the thus configured optical transmitter/receiver 900, however, due to the fixed connection via the metal flange 10 between the optical semiconductor element module 6 and the electrically conductive casing 9, heat generated in the electronic circuit board 7 firmly retained in the electrically conductive casing 9 can be transferred to the optical semiconductor module 6 by way of the metal flange 10, whereupon a variance of temperature arising from this heat may induce a degradation or a variation of characteristics of the optical semiconductor element module 6, making it difficult to obtain an optical transmitter/receiver exhibiting stable performance.
The present invention was conceived in order to solve the above problems. It is therefore an object of the present invention to provide a highly reliable optical transmitter/receiver using a resin flange for firmly fastening an optical semiconductor element module and an electrically conductive casing together, to thereby keep heat insulating properties between the optical semiconductor element module and the electrically conductive casing and present excellent and stable performances.
According to one aspect of the present invention there is provided an electronic apparatus comprising an electronic circuit board; an electrically conductive casing for encasing the electronic circuit board; a semiconductor element module electrically connected to the electronic circuit board; and a resin fixture intervening between the electrically conductive casing and the semiconductor element module, the resin fixture mounted with the semiconductor element module and fitted to the electrically conductive casing.
The electronic apparatus of the present invention allows the resin fixture to intervene between the electrically conductive casing and the semiconductor element module so as to be able to suppress transfer of heat generated in the electronic circuit board to the semiconductor element module. It is thus possible to suppress degradations and variations of characteristics of the semiconductor element module. As a result, an electronic apparatus having superior and stable performances can be provided.
In the electronic apparatus of the present invention, the resin fixture may have a notched portion formed in its outer wall, and the electrically conductive casing may be formed with a hooked portion which fits into the notched portion. The resin fixture may have a protrusion formed on its outer wall, and the electrically conductive casing may be formed with an insertion aperture for receiving the protrusion. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding. It is thus possible to reduce the number of assembling steps and the number of components.
In the electronic apparatus of the present invention, the semiconductor element module may have a raised portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a recessed portion formed in its inner surface at a site where the semiconductor module is mounted, the recessed portion being fitted to the raised portion. This enables the semiconductor element module to easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the semiconductor element module may have an externally threaded portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have an internally threaded portion formed in its inner surface at a site where the semiconductor module is mounted, the externally threaded portion being screwed into the internally threaded portion.
In the electronic apparatus of the present invention, the semiconductor element module may have a recessed portion formed in its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a raised portion formed on its inner surface at a site where the semiconductor module is mounted, the raised portion being fitted to the recessed portion.
In the electronic apparatus of the present invention, the resin fixture may have a metal-plated outer surface. This enables the resin fixture to serve as an electromagnetic shield for the semiconductor element module so that an electronic apparatus having more stable performances can be provided.
In the electronic apparatus of the present invention, the electronic circuit board may be bonded to and encased in the electrically conductive casing by use of an electrically conductive adhesive, such as an adhesive sheet. This enables heat generated in the electronic circuit board to be transferred by the electrically conductive adhesive sheet to the electrically conductive casing so that a high-performance electronic apparatus having an increased allowable heat value can be provided.
In the electronic apparatus of the present invention, the semiconductor element module is preferably an optical semiconductor element module.
In the electronic apparatus of the present invention, the semiconductor element module may have a raised portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and have a recessed portion formed in the inner surface at a site where the semiconductor module is mounted, the recessed portion being fitted to the raised portion. The electrically conductive casing may be formed with a hooked portion which fits the notched portion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the semiconductor element module may have an externally threaded portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and have an internally threaded portion formed in its inner surface at a site where the semiconductor module is mounted, the externally threaded portion being screwed into the internally threaded portion. The electrically conductive casing may be formed with a hooked portion which fits the notched portion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the semiconductor element module may have a recessed portion formed in its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and have a raised portion formed on its inner surface at a site where the semiconductor module is mounted, the raised portion being fitted to the recessed portion. The electrically conductive casing may be formed with a hooked portion which fits the notched portion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the semiconductor element module may have a raised portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a protrusion formed on its outer surface and have a recessed portion formed in its inner surface at a site where the semiconductor module is mounted, the recessed portion being fitted to the raised portion. The electrically conductive casing may be formed with an insertion hole which receives the protrusion of the resin fixture.
In the electronic apparatus of the present invention, the semiconductor element module may have an externally threaded portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a protrusion formed on its outer surface and have an internally threaded portion formed in its inner surface at a site where the semiconductor module is mounted, the externally threaded portion being screwed into the internally threaded portion. The electrically conductive casing may be formed with an insertion hole which receives the protrusion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding.
In the electronic apparatus of the present invention, the semiconductor element module may have a recessed portion formed in its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a protrusion formed on its outer surface and have a raised portion formed on its inner surface at a site where the semiconductor module is mounted, the raised portion being fitted to the recessed portion. The electrically conductive casing may be formed with an insertion hole which receives the protrusion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the resin fixture may have a notched portion formed in its outer wall and have a protrusion formed on its outer surface, and the electrically conductive casing may be formed with a hooked portion which fits the notched portion and with an insertion hole which receives the protrusion. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding.
In the electronic apparatus of the present invention, the semiconductor element module may have a raised portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and a protrusion formed on its outer surface and have a recessed portion formed in the inner surface at a site where the semiconductor module is mounted, the recessed portion being fitted to the raised portion. The electrically conductive casing may be formed with a hooked portion which fits the notched portion of the resin fixture and with an insertion hole which receives the protrusion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.
In the electronic apparatus of the present invention, the semiconductor element module may have an externally threaded portion formed on its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and a protrusion formed on its outer surface and have an internally threaded portion formed in the inner surface at a site where the semiconductor module is mounted, the externally threaded portion being screwed into the internally threaded portion. The electrically conductive casing may be formed with a hooked portion which fits in the notched portion of the resin fixture and with an insertion hole which receives the protrusion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding.
In the electronic apparatus of the present invention, the semiconductor element module may have a recessed portion formed in its outer surface at a site where the semiconductor element module is fitted to the resin fixture, and the resin fixture may have a notched portion formed in its outer wall and a protrusion formed on its outer surface and have a raised portion formed on its inner surface at a site where the semiconductor module is mounted, the raised portion being fitted to the recessed portion. The electrically conductive casing may be formed with a hooked portion which fits the notched portion of the resin fixture and with an insertion hole which receives the protrusion of the resin fixture. This enables the resin fixture to be fastened to the electrically conductive casing without screwing or bonding so that the semiconductor element module can easily be positioned relative to the resin fixture and the electrically conductive casing.